Gasification studies - Task 4 topical report, Utah Clean Coal Program, Reporting period October 2009 - July 2011

A key objective of the Task 4 activities has been to develop simulation tools to support development, troubleshooting and optimization of pressurized entrained-flow coal gasifiers. The overall gasifier models (Subtask 4.1) combine submodels for fluid flow (Subtask 4.2) and heat transfer (Subtask 4.3) with fundamental understanding of the chemical (Subtask 4.4) and physical (Subtask 4.5) processes that take place as coal particles are converted to synthesis gas and slag. However, it is important to be able to compare predictions from the models against data obtained from actual operating coal gasifiers, and Subtask 4.6 aims to provide an accessible, non-proprietary system, which can be operated over a wide range of conditions to provide well-characterized data for model validation. Highlights of this work include: • Verification and validation activities performed with the Arches coal gasification simulation tool (Subtask 4.1). The simulation tool was expanded to handle multiphase flow, and the various submodels required for coal gasification were implemented. Several aspects of the coal gasification model were continually improved, including the numerical behavior of the multiphase model, the direct quadrature method of moments (DQMOM) and the gas-phase combustion model, as well as the parallel scalability of the simulation tool. Validation activities included exploration of several novel statistical concepts applied to constructing surrogate models for expensive functions, all extremely useful in the validation process. Several input variables were investigated, and four were of primary importance, particularly the activation energy of the high-temperature devolatilization reaction (E2). • The development of a one-dimensional turbulence (ODT) model and associated validation activities; the exploration of principal component analysis (PCA) for use in developing combustion models; and the development of interfaces to enable the use of these models (Subtask 4.2). • The identification of data for verification of the Reverse Monte Carlo ray tracing (RMCRT) radiation algorithm (Subtask 4.3). This data includes analytical solutions to idealized scenarios as well as pseudo-exact solutions from well-accepted numerical benchmark cases. The RMCRT algorithm has proven to be an accurate way to solve for radiation under gasification conditions. This algorithm has demonstrated convergence with an increase in number of rays traced, and has been implemented into the ARCHES code. • The use of the Pressurized Flat-Flame Burner (PFFB) to study pyrolysis and CO2 gasification of four coals; the development of a model for coal swelling; and the study of soot formation from a coal tar surrogate with he PFFB (Subtask 4.4). • The study of the char-slag transition for three different coals, focusing on the morphology of the partly converted material and associated density and internal surface area. The results indicate that at conversions higher than roughly 95%, the material is completely coalesced, resulting in limited accessibility of the remaining carbon (Subtask 4.5). • The development, operation, and preliminary results from the University of Utah's pilot-scale entrained-flow coal gasifier.